The bright caterpillar at left is the caterpillar for the Black Swallowtail (Papilio polyxenes asterius). They love plants which belong to the fennel/dill/Queen Anne's lace type. Here, he is feeding on a red fennel which freely seeds itself in my garden...a little too freely, but I keep it around to feed these brilliant creatures.
Yesterday, one had the misfortune to take a swim in the pool. We fished him out and I carefully placed him on a daylily to let him dry out.
And yes, he is a him. The females don't have the yellow like this, but have more blue. There seems to be a bit of variation in patterning.
No doubt he will show up in a future quilt.